It is notoriously old in the art to reciprocate a downhole piston by utilizing a string of sucker rod in order to provide power by which fluid is lifted from a downhole fluid producing formation and uphole to the surface of the ground. It is also notoriously old in the art to use a continuous flow of fluid connected to a downhole hydraulic pump by means of a fluid conduit. Both of these pumping techniques include either a string of sucker rod or a separate power oil tubing string.
Hydraulically actuated downhole pumps of the type heretofore known have required a separate power oil string which extends downhole to the hydraulically actuated pump, and often a production string which leads back uphole to the surface of the ground through which the spent power fluid and the produced fluid flows. The present invention differs from the prior art in that the conduit leading downhole to actuate the downhole pump is also the conduit through which the produced fluid and spent power fluid return uphole to the surface of the ground. Such a pump is the subject of the present invention.